Research on attenuation characteristic of sound wave in coal or rock body

In order to using power sound wave increase permeability of coal, rules of attenuation of sound wave in coal should be studied. In this paper, characteristic and mechanism of attenuation of sound wave in coal was researched according to acoustic theory and attenuation coefficients was estimated by acoustic parameter of coal. The research results show that the main attenuation mechanism of sound wave in coal is absorption attenuation and scattering attenuation. The absorption attenuation includes viscous absorption, thermal conduction absorption and relaxation absorption. Attenuation coefficient of sound wave in gaseous coal is 38.5 Np/m. Researches on attenuation characteristic of sound wave will provide the theoretical basis for power sound wave improving permeability of coal and accelerating desorption of coal bed gas.

Relationships of the internodal distance of biological tissue with its sound velocity and attenuation at high frequency in doublet mechanics

In view of the discrete characteristics of biological tissue, doublet mechanics has demonstrated its advantages in the mathematic description of tissue in terms of high frequency （〉 10 MHz） ultrasound. In this paper, we take human breast biopsies as an example to study the influence of the internodal distance, a microscope parameter in biological tissue in doublet mechanics, on the sound velocity and attenuation by numerical simulation. The internodal distance causes the sound velocity and attenuation in biological tissue to change with the increase of frequency. The magnitude of such a change in pathological tissue is distinctly different from that in normal tissue, which can be used to differentiate pathological tissue from normal tissue and can depict the diseased tissue structure by obtaining the sound and attenuation distribution in the sample at high ultrasound frequency. A comparison of sensitivity between the doublet model and conventional continuum model is made, indicating that this is a new method of characterizing ultrasound tissue and diagnosing diseases.

Properties of sound attenuation around a two-dimensional underwater vehicle with a large cavitation number

Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wave propagation is studied to obtain the influence of bubbly liquid on the acoustic wave propagation in the cavity region. The sound attenuation coefficient and the sound speed formula of the bubbly liquid are presented. Based on the sound attenuation coefficients with various vapor volume fractions, the attenuation of sound intensity is calculated under large cavitation number conditions. The result shows that the sound intensity attenuation is fairly small in a certain condition. Consequently, the intensity attenuation can be neglected in engineering.

Frequency-selective attenuation of sound propagation and reverberation in shallow water

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Theoretical Calculation and Analysis of Muffler Based on Multilayer Sound Absorbing Material

The multilayer impedance composite sound absorption structure of the new muffler is proposed by combining the microporous plate structure with the resonant sound absorption structure of the porous material.Firstly,the acoustic impedance and acoustic absorption coefficient of the new muffler structure are calculated by acoustic electric analogy method,and then the noise attenuation is calculated.When the new muffler structure parameters change,the relationship among the noise frequency,the sound absorption coefficient and the noise attenuation is calculated by using MATLAB.Finally,the calculated results are compared with the experimental data to verify the correctness of the theoretical calculation.The variation of resonance peak,resonance frequency and attenuation band width of each structural parameter is analyzed by the relation curve.The conclusion shows that it is feasible to use multilayer sound absorbing materials as the body structure of the new muffler.And the influence relationship between the change of various parameters of the sound absorption structure with the sound absorption coefficient and noise attenuation is obtained.

Quiet in the nest:The nest environment attenuates song in a grassland songbird

The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecific animals early in life.In songbirds,nest structure varies considerably across species,and the resulting impact on sound transmission may have consequences for vocal learning in nestlings.In this study,we tested the hypothesis that the nest environment attenuates song of Savannah Sparrows(Passerculus sandwichensis),grassland songbirds that build nests on the ground under cover of dense vegetation.We recorded live Savannah Sparrows singing at variable distances from 21 nests.We recorded songs using one microphone inside the nest(the typical position of a nestling)and another placed 1 m directly above the nest(a typical position of an adult).We found a substantial reduction in signal-to-noise ratio,where songs recorded inside the nest were an average of 11 dB lower than songs recorded directly above the nest.We estimate that the attenuation imposed by the nest reduced the maximum acoustic environment from 117.7 m(for recordings above the nest),to 78.6 m(for recordings within the nest),which is analogous to listening from a position 39.1 m farther away from the singer.Previous research estimated that song transmits up to 100 m in this species,so any adult male within 100 m of a young bird was previously considered a potential vocal tutor.By reducing the nestling acoustic environment from 100 m to 78.6 m,the number of male tutors available to nestlings is reduced by an average of 27%.Given the growing evidence that song learning begins very early in life,future research on vocal development should account for how the structural properties of the natal environment affect the songs that nestlings hear.

Ultrasonic Resonator Techniques for Broad-band Spectroscopy and for High-resolution Sound Velocity Measurement of Liquids

This review gives a short introduction into the principles of ultrasonic measurement techniques for liquids, using cavity resonators. Guidelines for the resonator design in broad-band ultrasonic stxctroscopy as well as in high-resolution single-frequncy or narrowband applications are presented. Deviations of the field configuration in real cells frtxn that in an ideal resonator are discussed and relations for the mode spectrum of cavity fields are given. Recent resonator measurement procedures and methods of data evaluation are mentioned briefly. Some examples of measurements show the extended usability of ultrasonic resonator techniques in basic science and in a wide range of applications for rrkaterials characterization, in manufacturing processes, as well as in control routines.

以声场测听方法评估插入式耳机和头戴式耳机的衰减值

目的研究在声场测试中,头戴式耳机和插入式耳机对不同频率声音的衰减作用。方法选取40名健听人,在声场条件下测试双耳裸耳听阈及双耳分别佩戴头戴式和插入式耳机双耳听阈,耳机均不给声。比较在声场条件下不同类型耳机对不同频率声音的衰减作用。结果头戴式耳机在0.25~8 kHz每倍频程的声音衰减值分别为6.13±2.40 dB HL、7.00±3.36 dB HL、12.50±3.92 dB HL、18.75±5.03 dB HL、28.25±6.56 dB HL、17.50±5.99 dB HL;插入式耳机在0.25~8 kHz每倍频程的声音衰减值分别为16.88±5.27 dB HL、18.13±5.27 dB HL、22.38±4.08 dB HL、31.25±4.49 dB HL、36.13±5.49 dB HL、35.50±6.68 dB HL。结论两种不同类型耳机对不同频率声音的衰减均有显著效果,对声音的衰减值随着频率的升高而增加,在1~8 kHz范围内效果更显著,插入式耳机的衰减效果明显优于头戴式耳机。

超声检测DZ-I国家标准样品研制及测定方法研究

研制无损检测标准样品能够统一检测标准、提高检测精度、保证产品质量。本文借鉴普通标准样品制备技术,结合无损检测的超声波检测标准试块专用标准样品的技术特点,制备了DZ-I标准样品试块,并测定其化学成分、晶粒度、尺寸;选定用声速和声衰减作为DZ-I标准样品试块的定值参数,并采用水浸脉冲反射法、多次反射回波法测量和计算参数。结果显示:DZ-I标准样品试块满足标准要求;测试试块的声速和声衰减可保证DZ-I标准样品试块的一致性与稳定性。在实际应用中,使用这样的标准样品可为超声无损检测过程提供准确可靠的技术依据,确保检测结果的准确性和一致性。

缆控式海底沉积物声温同步探测取样系统研发与应用

为精确测量海底浅表层沉积物声学及温度参数,自主研发了一种缆控式海底沉积物声温同步原位探测取样系统。与国内外传统的沉积物声学原位探测系统相比,该系统能够完成深海浅表层沉积物声速、声衰减等声学参数以及多点位温度的原位实时测量,同时实现了可视化同步精准取样。整套系统以5个单元为基础构建,包括声学参数原位测量系统、多点位温度梯度探测系统、浅表层沉积物取样系统、固定组件以及实时通讯控制系统,实现了声波发射和接收、沉积物取样、多点位温度探测等关键技术的融合。本套系统于2022年5月在台西南盆地进行了海试应用,成功获取了试验区域海底浅表层沉积物的声速、声衰减系数、温度梯度等原位参数。海试结果表明,该系统工作稳定,声速测量精度小于2%,原位温度梯度精度误差小于0.001℃。同时,获取低扰动高保真的原位柱状沉积物样品共计超过3 m,用于后期实验室与原位测量的对比分析。该系统的成熟应用,有助于提高海底浅表层沉积物声学参数的探测效率与精度。

有源降噪入耳式耳机声衰减实验测量及对比研究

针对有源降噪入耳式耳机声衰减测量,对比研究了4种典型的测量方法,包括真耳听阈衰减法(REAT)、等响法(LB)、真耳内置传声器法(MIRE)和专用声学测试装置法(ATF)。依据该类耳机的特点设计了测量装置、实验环境和实验方案,开展了3款耳机的测量研究。结果表明,对于无源声衰减测量, MIRE方法与作为护听器“黄金”标准的REAT方法相比,中高频差异在±3 dB范围内,而MIRE方法在低频更准确;对于有源声衰减测量, MIRE方法与LB方法的结果接近,差异在±2 dB范围内,且MIRE方法更易于操作。MIRE方法有较高的测试效率和准确性,是测量有源降噪入耳式耳机声衰减的一种有效方法。

基于多物理场耦合的变压器噪声及降噪措施研究

随着电压等级、变压器的容量以及数量的不断提升,变压器的噪声污染日益严重,采取有效措施降低变压器噪声已迫在眉睫。基于有限元仿真平台搭建了110 kV系列变压器模型,采用电-磁-力-声多物理场耦合的方法对不同容量变压器的声压级分布以及应力分布情况进行仿真分析,揭示了不同容量变压器噪声与磁通密度、磁致伸缩效应等参数的关系,依据所得结果提出了基于改进变压器铁心材料和改变铁心夹紧力等方法的降噪措施。

充液管中的导波测量海底沉积物原位声速的方法研究

海底沉积物原位声学参数是标定海底地层声场环境、开展多种海洋工程应用的关键参数之一。本文首先建立了充液管-地层物理模型中声波传播的有限差分算法,数值模拟并分析了管中接收声波的特征及其随沉积物速度的变化规律,着重分析了首波的传播特性随距离的变化特征;其次,在此基础上研制了可挂接于海底静力触探装置的实验样机及其核心部件,如声波发射和接收换能器及功能电路板等,搭建了实验测试平台并进行了相关的性能实验测试,对管外存在不同介质下管中激发产生的导波的声信号特征进行了对比和分析。理论和实测结果表明:充液管中导波的衰减特性受到沉积物声速的影响,该特性可用于反演测量地层的声速,实验测量的结果进一步论证了方法的可行性。

Low-frequency hybridized excess vibrations of two-dimensional glasses

One hallmark of glasses is the existence of excess vibrational modes at low frequenciesωbeyond Debye’s prediction.Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight into the anomalous mechanical and thermodynamic properties of glasses.However,there is still intensive debate as to the frequency dependence of the population of low-frequency excess vibrations.In particular,excess modes could hybridize with phonon-like modes and the density of hybridized excess modes has been reported to follow D_(exc)(ω)~ω^(2)in 2D glasses with an inverse power law potential.Yet,the universality of the quadratic scaling remains unknown,since recent work suggested that interaction potentials could influence the scaling of the vibrational spectrum.Here,we extend the universality of the quadratic scaling for hybridized excess modes in 2D to glasses with potentials ranging from the purely repulsive soft-core interaction to the hard-core one with both repulsion and attraction as well as to glasses with significant differences in density or interparticle repulsion.Moreover,we observe that the number of hybridized excess modes exhibits a decrease in glasses with higher density or steeper interparticle repulsion,which is accompanied by a suppression of the strength of the sound attenuation.Our results indicate that the density bears some resemblance to the repulsive steepness of the interaction in influencing low-frequency properties.

Fine Sand and Clay Sediment Acoustic Properties of the Novel Sediment Sample from the Arabian Sea:Experimental Investigations and Biot−Stoll Model Validation

The present study explores the physical and acoustic characteristics of fine sand and clay in novel seabed marine sediments from of Pakistan coastline of the Arabian Sea.The measured physical parameters included mean grain size,mass density,bulk density,salinity,porosity,permeability,pore size and mineralogical composition.Acoustic properties,including sound speed and attenuation,in the high frequency range of 90-170 kHz were analyzed.A controlled laboratory setup with the acoustic transmission method and Fourier transform techniques was utilized to examine the sound propagation and absorption of novel seabed sediments.The standard deviation of mean sound speed in fresh water was 0.75 m/s,and attenuation was observed in the range of 0.43 to 0.61 dB/m.The mean sound velocity in sand and clay varied from 1706 to 1709 m/s and 1602 to 1608 m/s,respectively.Corresponding average attenuation was observed at 80 to 93 dB/m in sandy sediments and from 31.8 to 38.6 dB/m in clayey sediments.Sound velocity variation within sandy sediment is low,consistent with expected results,and smaller than the predicted uncertainty.However,clay sediment exhibited a positive linear correlation and low sound speed variation.Attenuation increased linearly with frequency for both sediments.Finally,the laboratory results were validated by using the Biot−Stoll model.The dispersion of sound speed in sandy and clayey sediments was consistent with the predictions of the Biot−Stoll model.Measured attenuation aligned more with Biot−Stoll model predictions due to improved permeability,tortuosity and pore size parameter fitting.

井旁裂缝随钻声波测井响应的数值模拟研究

裂缝是油气运移的重要渗流通道和储集空间,为研究井旁水平裂缝对声波响应的影响,采用薄平板流体层裂缝模型,利用有限元数值模拟含有水平裂缝地层的声波全波列响应。在10~25 kHz频段内进行裂缝性地层反射声场的数值模拟,优选出冲激声源的最佳激发频段,研究不同源距下全波列中斯通利波的衰减系数及不同裂缝宽度对斯通利波的影响。结果表明,在最优激发频率20 kHz下,当源距为4 m时反射波相对幅值较大,源距为4.5 m时直达斯通利波的衰减最大;裂缝宽度越大,斯通利波的衰减越大、反射斯通利波及反射横波的幅度越大;接收器距离裂缝越近,反射斯通利波与反射横波的幅度越大。

琼脂凝胶中气泡含量及间距对超声波衰减特性的影响

首先,基于声学探伤技术,采用透射法就琼脂凝胶中气泡对超声波传播的影响进行了试验研究;其次,用有限元分析软件对含气泡琼脂凝胶中的超声波传播进行了声学仿真。将试验结果和仿真结果进行对比,趋势一致结果符合良好,对琼脂凝胶中气泡尺寸、数量及间距对超声波衰减的影响分别进行了分析。结果表明:当气泡含量发生变化时,对超声波衰减起主要作用的是吸收衰减;当气泡含量一定时,气泡间距的改变对超声波的传播有着显著影响,随着间距的增加,声衰减逐渐增大,且随着频率增加声衰减逐渐减小。

中国近海主要表层沉积物类型的原位声学特性

海底表层沉积物的声学特性对于海洋声传播和声探测有重要影响。不同类型的海底沉积物表现出不同的声学特性。针对海洋声学研究对海底声学特性参数快速获取的需求,本文利用近年来获得的100个站位的声学特性原位测量和沉积物样品测试数据,统计了中国近海8种典型沉积类型的声速、声衰减系数等声学特性和平均粒径、密度等物理性质。通过与已有测量数据和统计结果的对比显示,其与多种原位测量系统获得的数据有很好的一致性,但Hamilton统计的声速比、声衰减因子等参数则显著偏高。基于VGS理论的频散模型计算结果表明:Hamilton统计结果的偏高并非完全由其较高的测量频率引起。对于缺少直接测量数据的海域,本文的统计结果提供了一种基于沉积物类型进行海底声学特性初步估计的方案。

基于海底沉积物重力柱状取样器的新型原位声学一体化系统研制

本文介绍了一种基于海底沉积物重力柱状取样器的新型原位声学一体化系统,名为海底沉积物原位声学与取样一体化系统(Sediment Acoustics and Sampling Integrated System,SASIS),该系统可以为海底区域地声模型研究和海洋工程地质评价等提供重要数据和样品。SASIS水下结构主要包括声学测量单元和重力柱取样单元,其发射换能器、接收换能器与重力柱状取样器实现一体化集成。系统利用振动滑行纵波方式测量沉积物的声速和声衰减,声波主频为12 k Hz、28 kHz可选,采用1发4收测量模式,在原位声学测量时可同步采集同一深度位置的沉积物样品。依托自然资源部第二海洋研究所-上海交通大学联合基金2023年度共享航次,SASIS在浙江舟山附近东海海域成功地进行了5站试验,试验站位水深约12.0 m,SASIS系统高效地同步采集了原位测量数据和沉积物样品。本文对沉积物声速和声衰减进行了初步数据分析,与前人测量数据、样品实验室声学测量结果对比表明,SASIS系统的原位声学数据可靠且有效。

基于数值仿真计算的高速铁路声屏障长度对插入损失的影响

在当前高速铁路降噪措施中,声屏障最为普遍和有效,其中声屏障设置高度是主要设计参数,而声屏障设置长度和位置,则一般根据经验结合简单计算选取,声屏障长度及预测点位置对插入损失变化的影响考虑较少。根据Kurze点声源绕射声衰减理论推导有限长声屏障对列车线声源插入损失的理论算法,对比分析声屏障长度、高度变化对不同位置预测点声屏障插入损失的影响。研究结论如下:(1)随着声屏障长度增加,各预测点位置尤其声屏障两端附近,声屏障插入损失变大;(2)采取加高、延长声屏障措施对于插入损失值及空间分布影响不同,应根据预测点位置情况合理选择声屏障优化措施;(3)半无限长声屏障端部加长50 m后,插入损失变化量较为明显的区域位于声屏障端部水平距离110 m、与线路中心线距离130 m范围内。